In the manufacture of paper products such as paper, cardboard, and the like from pulp, the strength properties of the final product can be increased by adding so called “paper strength agents.” Paper strength agents can also allow for a reduction in the overall basis weight of the paper product to achieve the same paper strength and thus save on the cost of cellulosic raw materials. Conventional paper strength agents include starches, urea/formaldehyde resins, melamine/formaldehyde resins, acrylamide copolymers, polyamidoamine/epichlorohydrin resins, carboxymethylcellulose, guar gum, and chitosan. Among these, the acrylamide copolymers and starches are the most often applied.
Paper strength agents are also used when preparing recycled paper products from waste paper. The paper strength agents help improve the durability of recycled product, which otherwise could be lacking given the properties of the waste paper raw materials. Cardboard is one such product that is often prepared from recycled paper. Approximately 70% of all corrugated cardboard is recycled and at least 50% of all new boxes come from recycled material. In China, nearly 100% of all boxes come from recycled material.
Cardboard can be recycled about six times before it becomes nearly useless. Thus the use of paper strength agents can help extend the life and usefulness of recycled cardboard products. Still, however, there is a need for new techniques and products for improving the durability of paper products, especially recycled products. The compositions and methods disclosed herein address these and other needs.